This invention relates to colored article such as a color member, a color filter for a multicolor display and, a multicolor pattern on a substrate or the like, and to a method for manufacturing the colored article, and more specifically to a method for manufacturing a multicolor display device having color filters made of polymer layers formed by electrodeposition.
Generally, methods known in the art for forming multicolor patterns on, for example glass substrates, including coloring a glass substrate by surface-diffusion of metallic ions, coloring a glass substrate by printing and baking low-melting fritted glass, and coloring a glass substrate by forming printed pattern by screen printing with an ink containing an organic high-polymeric binder.
These methods have both merits and demerits. For example, the coloring by diffusion of metallic ions allows the glass surface to retain flatness but involves a complex process and fails to color the object in a desired hue.
The method dependent on printing has drawbacks that printing on glass is difficult, and the resultant colored layers themselves lack uniformity and transparency.
Other disadvantages common to these methods are growing difficulties to be encountered in producing finer patterns with a large number of colors and the tendency of misalignment of designs or deviation from the desired pattern position.
When substrates other than glass are used, printing and other techniques are also available for obtaining multicolor patterns. Here again finer and more-colored patterns than usual are extremely difficult to make.
Among the means to obtain fine patterns is one making use of photolithography. In that case, too, each color changeover requires a photolithographic step to be taken until a multicolor pattern is obtained, thus making the process quite complex.
FIG. 1 shows an example of a multicolor display device using color filters, wherein numeral 1 denotes a transparent substrate, 2a, 2b and 2c denote display electrodes composed of a transparent electroconductive film patterned in a desired figure or letter, 3a, 3b and 3c denote color filters formed in close contact on the surface of the display electrode 2a, 2b and 2c, respectively, 4 denotes a transparent counter electrode, and 5 denotes a transparent counter substrate. A material serving as an optical shutter made of liquid crystal or electrochromic material and opened or closed by an applied voltage is filled in the space between the two substrates 1 and 5. Color filters 3a, 3b and 3c are in different color tones. When a voltage is selectively applied between the display electrodes 2a, 2b and 2c and the counter electrode 4, a multicolor display is made.
A multicolor display using color filters is highly effective for practical use because the method is simple, free color tones can be easily obtained, and color filters can be combined with various display materials and systems.
However, when a multicolor display device using color filters are to be manufactured, care must be taken to align the patterns of the display electrodes and the color filters formed thereon with each other. Especially when a color graphic display of fine patterns in three primary colors is intended, alignment between the patterns of the display electrodes and the color filters is an important production problem involving difficulties. Color changeover for the multicolor feature is another factor that makes the process complex. Further, when the coloring is performed with dyes, an intermediate step of resist-coating treatment becomes necessary to avoid redyeing of previously colored area, thus adding to the complexity of the process. The choice of the resist-coating technique itself is a knotty problem as it varies with the type of dye to be employed.
Generally, the methods for producing color filters so far contrived have utilized screen printing, photolithographic, and other similar means. Screen printing requires no resist-coating but is not suitable for fine patterning; the more the number of colors, the lower the accuracy of the printing position, with the printed pattern increasingly being misaligned with the display pattern. Photolithography permits fine pattern but necessitates a photolithographic step for each color changeover and also a resist-coating treatment to prevent double dyeing. Consequently, the extreme complicacy offsets the advantages of the process as a simple multicoloring means.
In view of this, the present inventor proposed in Japanese patent application Nos. 233933/1982 and 233934/1982 the manufacture of color filters and of a multicolor pattern by a method of forming colored layers from solutions of a polymer and a coloring matter by electrodeposition using electrically conductive thin films on a substrate as electrodes. It was intended to provide a method for manufacturing a multicolor display device in a simplified way so that there is no misalignment of pattern with whatever fine display pattern, color changeover is possible without the need of any special resist-coating treatment, and strong, durable color filters are obtained.
However, a certain physical retention of the coloring matters in the colored layers can be obtained, where the layers are in contact with a liquid crystal or other chemical substance so that the transfer of the coloring matter to the liquid crystal from the layers, or loss of color occurs, thus marring the reliability of the display device.